Algal cells are a promising source of biofuels (Wijffels & Barbosa (2010) Science 329:796-99). Their ability to harness solar energy to convert carbon dioxide into carbon-rich lipids already exceeds the abilities of oil-producing agricultural crops, with the added advantage that algae grown for biofuel do not compete with oil-producing crops for agricultural land (Wijffels & Barbosa, 2010). In order to maximize algal fuel production, new algal strains will need to be engineered for growth and carbon fixation at an industrial scale (Wijffels & Barbosa, 2010). The identification of feasible regulatory elements is important to drive optimal protein expression relating to biofuel production in recombinant algae.
A Kozak sequence is a short consensus sequence centered around the translational initiation site of eukaryotic mRNAs that allows for efficient initiation of translation of the mRNA. The ribosomal translation machinery recognizes the AUG initiation codon in the context of the Kozak sequence, which differs among different phylogenetic groups. A sequence around the site of translational initiation that poorly matches the Kozak consensus for a species can reduce the level of translation and may result in the use of alternate or cryptic translational start sites that can interfere with translation of the transcript's major open reading frame.
Different mRNAs of the same organism can have slightly different Kozak sequences with different variations with respect to a consensus Kozak sequence for the organism, and the amount of protein synthesized from a given mRNA depends in part on the Kozak sequence's “strength.” A Kozak sequence's strength depends, in turn, on the precise sequence of nucleic acids of which it is composed. Certain positions in the sequence are more important than others, for example, the “start codon” (adenine-uracil-guanine, abbreviated “AUG”) is the most important portion of a Kozak sequence because AUG is the actual initiation codon encoding an N-terminal methionine. The A of the AUG is referred to as position +1 of a Kozak sequence, the U as position +2, etc. There is no number zero, so the position immediately upstream of the A is position −1. In vertebrates, a “strong” Kozak sequence in vertebrates requires a G in position +4 and an A or G in position −3. A Kozak sequence without either a G in position +4 or an A or G in position −3 will be “weak” when used in vertebrate gene expression. A vertebrate Kozak sequence with a G in position +4, or an A or G in position −3, but not both, is said to be “adequate.” Other positions also have lesser effects on the comparative “strength” or “weakness” of translation from a given mRNA. See, Kozak (1986) Cell 44:283-92.
Kozak (1987) Nucleic Acids Res. 15:8125-48 first discovered the vertebrate Kozak consensus sequence by analyzing transcripts from vertebrate animals. Since then, investigators have identified a wide range of Kozak sequences, each unique to a particular class of organisms.
For example, Hamilton et al. (1987) Nucleic Acids Res. 15:3581-93 report a Kozak consensus sequence from yeast.
Lütcke et al. (1987) EMBO J. 6:43-48 1001 report a consensus Kozak sequences from terrestrial plants.
Joshi et al. (1997) Plant Mol. Biol. 35:993-1001 report a consensus Kozak sequences from terrestrial plants.
Bruchez et al. (1993) Fungal Genet. Newslett. 40:89-96 report consensus Kozak sequences from nuclear gene transcripts in Neurospora crassa. 
Ikeda & Miyaska (1998) Biosci. Biotechnol. Biochem. 62:2457-59 report consensus Kozak sequences from both nuclear and chloroplastic transcripts collected from Chlamydomonas reinhardtii. 
U.S. Pat. No. 7,449,568 to Fukuda et al. reports a possible Kozak sequence from Porphyra yezoensis. 
Briggs & Tachikawa (U.S. Pub. No. 2010/0306880) report a single eukaryotic Kozak consensus sequence.
Tsai & Li (U.S. Pub. No. 2011/0014708) report the use of a mammalian Kozak sequence to drive translation of transgene transcripts in Nannochloropsis oculata. 
However, to date, a Kozak consensus sequence in Nannochloropsis has not been identified.